1. Field of the Invention
Embodiments herein present a method for forming a poly filled substrate contact on a SOI structure.
2. Description of the Related Art
Unlike bulk silicon technology, silicon on insulator (SOI) technology requires substrate contact through buried oxide (BOX), which can result in additional process steps. Poly fill and chemical mechanical polishing (CMP) are typical methods for forming a body contact. However, the CMP process is a costly process that can cause polishing scratches, which results in poor yield.
More specifically, FIGS. 1(a) to 1(e) illustrate a conventional process for forming a substrate contact on a SOI structure. The process begins by performing a shallow trench isolation (STI) process, comprising oxide filling and oxide CMP (FIG. 1(a)). Additionally, the STI process includes pad oxide and pad nitride formation, as well as active area patterning. Next, a substrate contact hole is made through STI oxide and BOX with litho/dry etching (FIG. 1(b)). Polysilicon is then formed over the structure with a low pressure chemical vapor deposition (LPCVD) process (FIG. 1(c)). Following this, the polysilicon is polished via CMP (FIG. 1(d)). As described above, the CMP process is a costly process that can cause polishing scratches, which results in poor yield. Finally, a shallow polysilicon recess is formed to a desired level with a dry etching method (FIG. 1(e)).